Standard Chartered Bank — illegal a4interest on credit card

Address:

201309

I have 2 credit cards in standard chartered - one ultimate credit card and another one supplementary.in the latest statement, i noticed an 'a4interest' charge even though i paid all my dues well before time. I even double checked all my credit payments - all of them either matches or is more than the bill i received. Looking at the other complaints it looks like stanc does it quite regularly to a lot of customers and is quite used to such fraudulent behaviour.